Gem Diamonds announced on Monday that it had uncovered two diamonds bigger than 100 carats at its Lesotho mine.
The find gives the company a good start to the year, with stock prices rising as much as 8.2 percent in London trading following the announcement.
It also follows on a good 2017, which saw the company unearth at least seven stones that exceeded 100 carats, and an improvement on 2016 which saw five unearthed.
The two diamonds, 117 carat and 110 carat D colour Type IIa diamonds were discovered at the Letseng mine in Lesotho. Type IIa diamonds are the most expensive stones as they contain little to no nitrogen atoms.
Letseng is renowned for the quality and size of the stones it produces, with the largest being the 603 carats Lesotho Promise unearthed in 2006. In 2015, a 357-carat stone was unearthed and sold for $19.3-million (around R235-million).
Monday seemed to be the day to announce big diamond discoveries as Lucapa Diamond Company also shared the discovery of 103 carats and 83-carat diamonds at its Angola operations.
Lucapa recorded its biggest ever in 2016 with a 404 carat stone that sold for $16-million (around R198-million).